Method for making a plastic thread



May 23, 1961 BECKER 2,985,503

METHOD FOR MAKING A PLASTIC THREAD Filed April 8, 1959 r 2 Sheets-Sheet l May 23, 1961 BECKER 2,985,503

METHOD FOR MAKING A PLASTIC THREAD Filed April 8, 1959 v 2 Sheets-Sheet 2 1 HI M l S 'u Q q 2. N O O a w (a, m

I \l m N United States Patent 'METHOD FOR MAKING A PLASTIC THREAD Hermann Becker, Raesfeld, Kreis Borken, Westphalia, Germany Filed Apr. 8, 1959, Ser. No. 804,910

Claims priority, application Germany Apr. 9, 1958 7 Claims. (Cl. 18-54) The invention relates to plastic filaments adapted for textile fabrics and to processes for the production of such plastic filaments.

A plastic filament for textile fabrics normally consists either of one monofilar fibre or of relatively short staples of monofilar fibres which are spun together.

It is an object of the invention to provide a filament of a hydrocarbon plastic, which is different from the above-indicated types of filaments and which can be easily made and which has small weight and high resistance against wearing. To this end the invention contemplates a flat filament folded irregularly in its longitudinal direction.

Still another object of the invention is to provide a fabric made of said filaments, said fabric being impermeable to water but permeable to air. Another object of the invention is to provide a process to manufacture said filaments readily.

Other objects, features and advantages of the invention will become apparent from the following description, which refers to the accompanying drawings illustrating two preferred embodiments of the invention.

In the drawings:

Fig. 1 is a side elevation view of an apparatus for manufacturing filaments of the invention;

Fig. 2 is a plan view of this apparatus;

Fig. 3 shows a filament according to the invention on enlarged scale;

Fig. 4 shows diagrammatically a fabric made of such filaments.

Fig. 5 shows an elevation of a part of a modified apparatus for manufacturing such filaments.

The filament according to this invention is made out of a thin strip or of a thin foil of plastic material adapted to be formed as a thin foil, strip or tube; eg a polyvinyl chloride or a polyethylene. The strip may have the form of a flat band having a width of a fraction of an inch such as, for example, Av-Vz inch, or of a band closed to a tube having a diameter of, for example, Ai inch; it may have a thicknes of one hundredth of an inch or less.

In Figs. 1 and 2, the apparatus consists essentially of three pairs of rollers 1, 2; 3, 4 and 5, 6, a rail 7 which can be heated and which is disposed between the pairs of rollers 1, 2 and 3, 4, a liquid container 8 with guide rollers 9, 10, 11, 12 and a winding means 13, as well as a number of knives 14.

A foil 15, which can be taken for example directly from an extruder and which is, for example polyethylene inch thick, is moved through the pair of rollers 1, 2 in the direction of the arrow P. In this movement, it is divided by the knives 14 into strips 16 of a constant breadth of 3 /2 inch. The strips 16 are drawn by the pair of rollers 3, 4 through nozzle-shaped slots 17 in the rail 7. These slots have a rectangular cross-section of such a size that the individual strips 16 are folded over somewhat irregularly in each nozzle 17. The breadth of "ice the folded strip may be one half up to one third of the breadths of the unfolded strip. For processing strips of 6 mm. breadth the cross-section of a slot may, for example, be 0.1 x 0.02 inch. The strips 19 thus folded enter the liquid container 8, which is filled with water at a temperature of from 80 to approximately 100 C. The strips 19 initially travel over a roller 9 which is outside of the liquid, then beneath two rollers 10 and 11, which are approximately half immersed in the water and then leave the container 8 after pasing over a roller 12 which is not in the water. The strips are then gripped by the pair of rollers 5, 6, the peripheral speed of which is about 3-4 times faster than the peripheral speed of the pair of rollers 3, 4. Because of this difference in the peripheral speeds, the strip which is in the liquid of the container 8 is stretched to 3-4 times its length. Each of the strip 20 which are stretched in this way is then wound on a conicalbobbin 13. 'Each of the conical bobbins 13 has its own drive means and a thread guide 21 so that the winding speed is constant. The stretching can under certain circumstances be of such a degree that a part of the strip becomes fibrous. The breadth of the strip 16 is decreased by the stretching. A strip out :8 mm. broad may be narrowed by the slot to 3 mm. and by the stretching to a fiat filament of 1 mm. breadth and approximately 0.2 mm. thickness.

The uniform heating of the rail 7 is obtained by dipping the lower end of the rail 7 into a glycerine bath 18 at a temperature of approximately 7080 C.

The apparatus can of course be modified according to dififerent requirements and materials. In many cases, it is advisable to guide the strips 19 through a hot air duct between the pairs of rollers 3, 4, and 5, 6 instead of through a water bath.

In Fig. 5, an extruder 21 extrudes several small tubes 22 of polyethylene. Each tube may have a diameter of V 4 and a wall of V or less. The tubes 22 are transported by a pair of rollers 27, 255 having essentially the velocity of extrusion. The tubes 22 are then fed into slots 23a, 25a, 26a of three rails 23, 25, 26 respectively which rails dip into a glycerine bath 24 of approximately 70-80 C. The base of the slots 23a, 25a, 26a is fiat, its width decreasing from rail 23 to rail 26; this width may for instance be the following: slot 23a /2", slot 25a slot 26a In these slots the tube is flattened and folded longitudinally. The resulting strip 22a is transported by a pair of rollers 29, 30 into a bath 8, as shown in Figs. 1 and 2. The circumferential speed of the rollers 29, 30 exceed the circumferential speed of the rollers 27, 28, thereby exerting a stretching force on the tube 22 and the strip 22a. This stretching may be up to or more; for instance half of the whole stretching of 300% may be done between the rollers 27, 28 and 29, 30 while the other half is done in the bath 8.

The slots 23a, 25a and 26a are situated slightly above a line connecting the gripping points of the rollers 27, 28 and 29, 30. Therefore these slots have the form of slits in the top of the rails 23, 25, 26. These slits enlarge towards their respective mouths and towards the top of the rails.

A fabric made of such polyethylene filaments has a tensile strength and resistance to abrasion which are considerably greater than that of a linen or cotton fabric of the same weight. The fact that such a fabric has a high degree of transparency can be desirable in many cases. If it is desirable to prevent such transperancy the foil, strip or tube may be dyed.

A fabric of such filaments, and especially of such polyethylene filaments is particularly usable for tents and awnings. For such purpose it may be made practically water-tight by exposing the fabric to a temperature of aesaeoa 3 1004 0 for about 15-100 seconds (this time being more especially dependent on the thickness of the fabric) and to hold the fabric during this time under the resulting shrinkage tension. The fabric has in fact'a tendency to shrink during such a treatment. It is generally advisable to permit a certain degree of shrinkage, but the fabric should be so held that it cannot yield completely to the shrinkage tension being set up. For example, this treatment of the fabric takes place on a tentering frame in such a way that it travels through a heating path with a length of 6 meters, at a speed of 12 m./ min. These temperatures and times are of course dependent on the plastic being used and the thickness of the textile mat.

rial.

The temperature is in addition dependent to a certain degree on the speed of travel, in that it must generally be higher in proportionas the residence time of the material in the heating zone is shorter. By such treatment the fabric can be made Watertight but permeable to air.

What is claimed is:

l. A process for producing a plastic filament comprising irregularly folding a fiat plastic strip by drawing the same through and against the bottom and sides of a slot, while subjecting said strip to heat and then stretching the folded strip by heating and placing the same under longitudinal tension, thereby producing a plastic filament.

2. A process as claimed in claim 1 comprising rolling the strip before placing the same under tension.

3. A process as claimed in claim 2 comprising supply- 4 ing the strip for drawing through the slot by flattening a tube of said plastic.

4. A process as claimed in claim 2 comprising cutting the flat strip from a larger strip of said plastic and sirnu1- taneouslycutting other flat strips from said larger strip and identically processing said other strips.

5. A process as claimed in claim 2 comprising succesively passing said strip through a series of slots including the first said slot, the slots being of successively narrowing breadth.

6. A process as claimed in claim 2 comprising weaving the filament into a fabric, heat treating the fabric, and supporting the fabric to substantially avoid shrinkage during the heat treatment.

7. A process as claimed in claim 2 wherein the width of the strip after it passes through the slotis about /3 to /2 of its width before it is passed through the slot.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A PROCESS FOR PRODUCING A PLASTIC FILAMENT COMPRISING IRREGULARLY FOLDING A FLAT PLASTIC STRIP BY DRAWING THE SAME THROUGH AND AGAINST THE BOTTOM AND SIDES OF A SLOT, WHILE SUBJECTING SAID STRIP TO HEAT AND THEN STRETCHING THE FOLDED STRIP BY HEATING AND PLACING THE SAME UNDER LOGITUDINAL TENSION, THEREBY PRODUCING A PLASTIC FILAMENT. 